The present technology includes improvements to, and in different embodiments makes use of, assignee's earlier work detailed in U.S. Pat. Nos. 6,122,403, 6,408,082 and 6,590,996, and published applications 20060115110, 20070189533, 20080112596, 20080300011, 20090116683, 20100046842, 20100048242, 20100150434, 20100317399, 20100261465, 20110098029, 20100165158, 20110098056 and 20100228632. The reader is presumed to be familiar with such prior work, and able to incorporate such teachings into implementations utilizing the presently-detailed technology.
Smartphones are increasingly being used with “visual search” applications. One visual search application decodes digital watermark data steganographically encoded (i.e., hidden) in printed imagery (such as in a magazine or on product packaging) and enables the phone to link to associated information and services, or take other action. Exemplary digital watermark technology, and visual search applications, are detailed in the above-cited patent documents.
Perspective distortion can sometimes interfere with proper decoding of digital watermark data. That is, if a watermarked object is imaged by a smartphone at a relatively large off-axis angle (e.g., greater than 15 or 30 degrees), the hidden watermark data may be sufficiently distorted by the perspective viewing angle that the decoding algorithm does not recognize it.
A related concern is consumer confusion. If a consumer uses a smartphone to image a magazine page, and no watermark is promptly detected, is it because the page does not include a watermark to which the smartphone should respond? Or is it because the magazine page is presented with an unsuitable perspective?
Accordingly, it is desirable to alert consumers of the presence of watermark data without requiring precise smartphone positioning.
It is also desirable to assist consumers in capturing imagery that has relatively little perspective distortion (e.g., less than 15 or 30 degrees).
In accordance with one aspect of the present technology, the presence of hidden data is reliably detected notwithstanding perspective angles exceeding 30, 45, or 60 degrees, or more.
In accordance with another aspect of the present technology, a smartphone provides feedback (e.g., on a display screen) that aids a user in positioning the smartphone so that the captured imagery has relatively little perspective distortion.
The foregoing and many other features and advantages of the present technology will be more readily apparent from the following detailed description, which proceeds by reference to the accompanying drawings.